Initial checkin of DefaultObservable: EXPERIMENTAL USE ONLY!

lib/python/OFS/DefaultObservable.py

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+##############################################################################
+__doc__="""Implement Observable interface (see
+http://www.zope.org/Members/michel/Projects/Interfaces/ObserverAndNotification)
+This class is intended to be used as a mixin (note that it doesn't derive
+from any Zope persistence classes, for instance).
+
+$Id: DefaultObservable.py,v 1.1 2000/06/09 16:46:37 tseaver Exp $"""
+
+__version__='$Revision: 1.1 $'[11:-2]
+
+import string
+from types import StringType
+
+class DefaultObservable:
+
+    def __init__( self, debug=0 ):
+        self._observers = []
+        self._debug = debug
+    
+    def _normalize( self, observer ):
+
+        # Assert that observer is a string or a sequence of strings.
+        if type( observer ) != StringType:
+            observer = string.join( observer, '/' ) 
+
+        return observer
+
+    #
+    #   Observable interface methods.
+    #
+    def registerObserver( self, observer ):
+
+        normal = self._normalize( observer )
+        if self.restrictedTraverse( normal, None ):
+            self._observers.append( normal )
+        else:
+            raise NameError, observer
+
+    def unregisterObserver( self, observer ):
+
+        self._observers.remove( self._normalize( observer ) )
+
+    #
+    #   Convenience method for derivatives.
+    #
+    def notify( self, event=None ):
+
+        bozos = []
+
+        for observer in self._observers:
+
+            obj = self.restrictedTraverse( observer, None )
+
+            if obj is not None:
+                try:
+                    obj( self, event )
+                except:
+                    bozos.append( observer ) # Veto not allowed!
+                    if self._debug:
+                        import traceback
+                        traceback.print_exc()
+            else:
+                bozos.append( observer )
+            
+        for bozo in bozos:
+            self._observers.remove( bozo )
+        
+
+#
+#   Unit tests
+#
+
+if __name__ == '__main__':
+
+    class DontGoHere( Exception ): pass
+        
+    class TestSubject( DefaultObservable ):
+
+        def __init__( self, paths ):
+            DefaultObservable.__init__( self, 0 )
+            self.paths = paths
+
+        def restrictedTraverse( self, path, default ):
+            return self.paths.get( path, default )
+
+    callbacks = {}
+
+    def recordCallback( name, subject, event ):
+        cbrec = callbacks.get( name, None )
+        if cbrec is None:
+            cbrec = callbacks[ name ] = []
+        cbrec.append( ( subject, event ) )
+        
+
+    class TestObserver:
+
+        def __call__( self, subject, event ):
+            recordCallback( 'direct', subject, event )
+        
+        def namedCallback( self, subject, event ):
+            recordCallback( 'named', subject, event )
+        
+        def named2Callback( self, subject, event ):
+            recordCallback( 'named2', subject, event )
+        
+        def boundCallback( self, subject, event ):
+            recordCallback( 'bound', subject, event )
+
+    def freefuncObserver( subject, event ):
+        recordCallback( 'freefunc', subject, event ) 
+    
+    def tryVeto( subject, event ):
+        """ Simulate attempted veto. """
+        raise 'Idawanna!'
+    
+    observer = TestObserver()
+
+    # Simulate Zope's path traversal mechanism.
+    paths = {}
+    paths[ 'direct'         ] = observer
+    paths[ 'direct/named'   ] = observer.namedCallback
+    paths[ 'direct/named2'  ] = observer.named2Callback
+    paths[ 'bound'          ] = observer.boundCallback
+    paths[ 'freefunc'       ] = freefuncObserver
+    paths[ 'tryVeto'        ] = tryVeto
+
+    subject = TestSubject( paths )
+
+    subject.registerObserver( 'direct' )
+    subject.registerObserver( 'bound' )
+    subject.registerObserver( 'direct/named' )
+    subject.registerObserver( ( 'direct', 'named2' ) )
+    subject.registerObserver( 'freefunc' )
+    subject.registerObserver( 'tryVeto' )
+
+    try:
+        subject.registerObserver( 'nonesuch' )
+        raise DontGoHere( 'path not found' )
+    except NameError:
+        pass
+    except:
+        import traceback
+        traceback.print_exc()
+
+    try:
+        subject.registerObserver( 3.1415926 )
+        raise DontGoHere( 'non-path' )
+    except TypeError:
+        pass
+    except:
+        import traceback
+        traceback.print_exc()
+
+    subject.notify( 'First event' )
+
+    subject.unregisterObserver( 'bound' )
+    subject.notify( { 'name' : 'Second event', 'value' : 42 } )
+
+    for key in callbacks.keys():
+        print '[%s]' % key
+        for cb in callbacks[ key ]:
+            print '    %s' % `cb`
+